1. Field of the Invention
This invention relates to a device for aligning one or more sheets, which is incorporated in a sheet handling device applied for a copying machine or the like, and more particularly to a sheet alignment device capable of exactly aligning sheets by pushing the sheets at the position close to the center of gravity thereof toward a predetermined aligning reference surface.
2. Description of the Prior Art
There has been known a sheet handling device generally so-called xe2x80x9csorterxe2x80x9d or xe2x80x9cfinisherxe2x80x9d for automatically sorting and stapling or punching sheets fed continuously from an image forming apparatus such as a copying machine and printer.
The sheet handling device as noted above has been usually provided with a device for aligning the sheets fed from the image forming apparatus so that the one side edges of the sheets are trued up with a predetermined aligning reference surface. The sheets stacked on an inclined tray are spontaneously aligned in one direction as the sheets slide down the slope of the inclined tray on account of their own weight, but they must be aligned by force in the direction perpendicular to that in which the tray is inclined.
A conventional way of aligning the sheets fed from the image forming apparatus such as the copying machine to the sheet handling device will be described with reference to FIG. 1A. As an illustration, the sheet handling device A has a tray T inclined upward in relation to a sheet introduction direction d1 in which the sheets are fed from the image forming apparatus M.
There is formed a sheet receiving wall F1 serving as a widthwise sheet aligning reference surface b1 vertically standing along the lower end (right end in the drawing) of the inclined tray T. The sheet s1 fed onto the inclined tray T spontaneously slides down the slope of the inclined tray in the opposite direction to the sheet introduction direction d1, and then, collides with the sheet receiving wall F1. In the same way, the following sheets fed from the image forming apparatus M also collide with the sheet receiving wall F1. As a result, all the sheets are automatically aligned in the sheet introduction direction d1.
The sheet handling device is provided with an aligning member PR for forcibly pushing the sheets toward a side wall F2 serving as a lengthwise sheet aligning reference surface b2 to align the sheets in the direction d2 (hereinafter, referred to as xe2x80x9caligning directionxe2x80x9d). That is to say, the sheet s1 fed onto the tray T is pushed against the lengthwise sheet aligning reference surface b2 of the side wall F2 by the aligning member PR. The sheets thus aligned may be bound by a stapler ST as occasion calls.
When the sheets are aligned in the aligning direction d2, it is desirable to push the sheets at the portion close to the center of gravity of the sheets (normally, the center of the sheets). In other words, the sheet s1 can be effectively pushed without strain with decreasing a deflection xcex41 from the center of gravity G1 of the sheet s1 to the point at which the sheet is pushed by the aligning member PR in the sheet introduction direction d1 in the system shown in FIG. 1A. If the sheets to be handled by the system are fixed in size, it is possible to minimizing the deflection xcex41. However, the sheets which are practically used are irregular in size and different in the center of gravity as a matter of course. When the sheet to be handled is large as shown in FIG. 1B, the deflection xcex42 between the center of gravity G2 of the sheet s2 and the point at which the sheet is pushed by the aligning member PR is increased, resulting in a large rotating moment r imposed on the sheet. Consequently, the sheet is liable to rotate on the tray during the aligning process.
When dealing with a sheet of small size (i.e. A4 size) as illustrated in FIG. 1A, the deflection xcex41 lessens to bring about a negligible rotating moment. However, the use of a sheet of large size (i.e. A3 size) causes large deflection xcex42 which entails a disadvantage such as failure in transporting the sheet and other possible accidents.
Specifically in a sorter for a copying machine handling sheets of various sizes, sheet alignment must be properly accomplished since its certainty inflicts on quality of the sheets finally obtained.
An object of the present invention is to provide a sheet alignment device capable of stably and exactly aligning sheets fed from an image forming apparatus.
Another object of the invention is to provide a sheet alignment device capable of exerting a pushing force on one or more sheets at a proper point determined according to the size of the sheet so as to suitably push the sheets against a sheet aligning reference surface without causing a rotational moment, thereby to stably align the sheets.
Still another object of the invention is to provide a high-efficient sheet alignment device having a driving system simple in structure, which can effectively exert a proper pushing force on sheets of different sizes to precisely align the sheets.
Yet another object of the invention is to provide a sheet alignment device capable of precisely handling and aligning sheets with high efficiency, which is applicable to not only various types of image forming apparatuses such as a copying machine, printer and facsimile, but also various sheet handling apparatuses such as a sheet stacker, sheet sorter and bookbinding apparatus.
To attain the objects described above according to the present invention, there is provided a sheet alignment device comprising a sheet storing unit; sheet aligning means including a movable aligning member which is movable back and forth toward a sheet aligning reference surface, and a variable push member movable in conjunction with the movable aligning member to push one or more given sheets in accordance with the size of the sheets; and means for moving the movable aligning member and variable push member in relation to the sheet aligning reference surface.
The movable aligning member and the variable push member which are operatively associated with each other are so arranged that when a given sheet is small in size, the movable aligning member is positioned so as to come into contact with the given sheet at a portion close to the center of gravity of the sheet of small size, and when the given sheet is large in size, the variable push member is positioned so as to come into contact with the given sheet at a portion close to the center of gravity of the sheet of large size.
During the aligning process, the movable aligning member moves toward the sheet aligning reference surface to exert the pushing force on the sheet or sheets no matter what the size of the sheet or sheets is.
When aligning one or more sheets of large size, the variable push member always comes into contact with the sheets to push the sheets toward the sheet aligning reference surface, but when aligning one or more sheets of small size, it is out of contact with sheets. The variable push member is selectively activated or deactivated by operation converting means in accordance with the size of the sheet to be handled so as to exert the pushing force on the sheets of large size or be out of contact with the sheets of small size. The operation converting means may be formed of an edge of an opening in a tray of the sheet storing unit, so that the variable push member operable in concert with the movable aligning member is brought in collision with the operation converting means to be retracted backward, when dealing with the sheets of small size.
Thus, the effective pushing point defined substantially by the region at which one or more sheets are efficaciously pushed by the associated movable aligning member and variable push member can be practically shifted to a position close to the center of gravity of the sheets.
The variable push member may be connected to the movable aligning is member by a hinge, or formed of resilient elastic material.
Between the movable aligning member and the variable push member, there may be interposed a medium-size sheet pushing element for aligning a sheet of medium size, so as to carry out a three-step aligning function. Such a three-step aligning mechanism makes it possible to enlarge the limits of permitting the sheets of minimum size to maximum size to be dealt with.
Other objects and features of the present invention will be hereinafter explained in detail with reference to the accompanying drawings.